Presence Of Sodium Silicate Research Articles

Innovative eco-friendly methyl orange removal: Mechanism, kinetic, and thermodynamic study using starch cryogel-integrated mesoporous silica nanoparticles

This study introduces a novel, eco−friendly composite, uncalcined mesoporous silica nanoparticles incorporated into a starch cryogel (MSNs-Cry), designed for the effective removal of methyl orange (MO) from water. MSNs−Cry integrates uncalcined mesoporous silica nanoparticles (MSNs) within a starch cryogel network, leveraging the high adsorption capacity of MSNs. The composite achieved a maximum adsorption capacity of 18.98 mg g⁻1 and demonstrated high removal efficiencies of 99.00 % ± 0.21 % in synthetic water (10 mg L−1 MO) and 92.77 % ± 1.76 % in real wastewater containing 0.43 mg L−1 MO. The Langmuir isotherm model provided a superior fit (R2 = 0.9930) compared to the Freundlich model (R2 = 0.9180), and the adsorption kinetics followed a pseudo−second−order model (R2 = 0.9917). The primary adsorption mechanisms included electrostatic attraction, hydrophobic interactions, and hydrogen bonding. The process was endothermic (ΔH° = 31.3 kJ mol−1), spontaneous, and more favorable at higher temperatures (ΔG° = −34.2 to −38.6 kJ mol−1 at 298–318 K). In the presence of sodium silicate at 13.1 times the MO concentration, removal efficiency drops by 35.77 %, and with sodium sulfate and urea at 100 times the MO concentration, it decreases by 8.65 %. Despite these challenges, MSNs−Cry effectively removes MO in the presence of the anionic dye Congo Red and metal ions, demonstrating its selective adsorption capabilities. The tablet form of MSNs−Cry prevents the loss of uncalcined MSNs, mitigating potential environmental and operational impacts. Additionally, the composite's effectiveness at a natural pH of 6.65 eliminates the need for pH adjustment, offering a cost−effective solution for real−world applications. This study establishes MSNs−Cry as a promising material for sustainable water purification.

Synthesis of carbon nanotube aerogels from cross-linked polyacrylamide/chitosan hydrogels via gamma irradiation for efficient oil removal

Environmental pollution, stemming from oil spills and improper disposal of organic solvents, severely threatens global water resources and ecosystems. This study addresses this concern by introducing carbon nanotube (CNT) aerogels as efficient adsorbents for removing pump oil and various organic solvents from water. Aerogels were synthesized from cross-linked Chitosan/polyacrylamide hydrogels using gamma irradiation in the presence of sodium silicate, incorporating varying concentrations of CNTs (1 %, 2 %, and 3 %). Characterization techniques, including FTIR, SEM, EDX, BET surface area analysis, and compression testing, unveiled the structural and physicochemical properties of the aerogels. Incorporation of CNTs substantially enhanced surface area and compressive strength, with the CNT 3 % aerogel exhibiting remarkable values (316 m2/g and 8.677 MPa, respectively). Hydrophobicity was confirmed by water contact angles (89° to 94°). The CNT aerogels demonstrated outstanding oil removal efficiency, reaching 93.15 %, surpassing the blank aerogel (38.01 %). The CNT aerogel achieved 80.68 % efficiency for methanol removal compared to 62.09 % for the blank aerogel. Kinetic studies revealed a chemisorption process, emphasizing the enhanced chemical interactions facilitated by CNTs. These findings underscore the promising potential of CNT aerogels for effectively removing oil and organic solvent contaminants from water, even at low concentrations.

Investigation of Inclusion States of Silicate and Carbonate Ions in Hydroxyapatite Particles Prepared under the Presence of Sodium Silicate.

Biological hydroxyapatite (HA) contains the different minor ions which favour its bio-reactivity in vivo. In this study, the preparation of HA particles containing both silicate and carbonate ions under the presence of sodium silicate was investigated, and the physicochemical properties were evaluated according to the contents and states of silicate and carbonate ions. The increment in the silicate ion reduced the crystallinity and expanded the crystalline size along with a-axis. Solid-state 29Si–NMR spectra indicated the increase in the adsorption of oligomeric silicate species on the HA particle surfaces in addition to the substitution state of silicate ions, suggesting the occurrence of the surface coating of silicates on the surfaces. The possible states of carbonate and silicate ions at the HA surfaces will provide the bioactivity.

Expanded graphite/paraffin/silica phase change composites with high thermal conductivity and low permeability prepared by the solid-state wet grinding method

In this study, expanded graphite (EG)/paraffin (PA)/silica (SiO2) composite phase change materials (PCM), with good thermal conductivity and impermeability, were fabricated for potential applications in solar energy. The EG-PA was first prepared by vacuum adsorption and then encapsulated by SiO2 through solid-phase wet grinding in the presence of sodium silicate. Our results show that the EG-PA-SiO2 composite have optimal properties when the mass ratio of raw material is PA: sodium silicate: H2O = 1:9:2:8. The latent heat of melting of the EG-PA-SiO2 composite prepared at this mass ratio is 106.2 J/g. The core material loss ratio, after washing with petroleum ether, is 4.79%. The thermal conductivity is 2.053 W/m·K, which is 8.5 times higher than that of pure paraffin wax, and the melt permeability is 9.35% after 120 min at 60 °C. Under simulated sunlight, the time required for the composite material to change from 30 °C to 65 °C is reduced by 70.78% compared to PA and the heat absorption and release times are nearly unchanged under multiple cycles. These results indicate that the material has a stable photothermal conversion efficiency.

Biomimetic spherical silica production using phosphatidylcholine and soy lecithin

Spherical silica particles are traditionally made via Stöber and modified-Stöber processes, which commonly use environmental toxins as reagents. Here we report a process to synthesise spherical silica particles using environmentally friendly biomolecules (phosphatidylcholine and soy lecithin) and employing water and soybean oil as solvents, rather than potentially harmful organic solvents. This scalable method represents an important step towards sustainable industrial silica syntheses. Under mildly acidic conditions phosphatidylcholine and soy lecithin can control the condensation of sodium silicate to form discrete, spherical silica particles. Silica particles with diameters ranging between 329 and 2232 nm were readily produced using phosphatidylcholine as the templating agent and soybean oil as the solvent in the presence of sodium silicate. Narrower size distributions (262–1272 nm) were achieved using soy lecithin as the templating agent in an aqueous acetate buffer solution containing sodium silicate. Silica particles grown using low concentrations of phosphatidylcholine and soy lecithin as templating agents formed by a combination of coalescence and Ostwald ripening, whilst particles grown at high concentrations predominantly formed through Ostwald ripening behaviour. The possibility of sustainably producing spherical silica particles in a simple biomolecule-templated synthesis is shown.

The Effect of Crystalline Waterproofing Admixtures on the Self-Healing and Permeability of Concrete.

This paper investigates the effectiveness of a specific crystalline waterproofing admixture (CWA) in concrete as a function of a water–binder ratio. Four concrete mixes with and without CWA were prepared; two of them with a water–binder ratio of 0.45 and two of them with a water–binder ratio of 0.55. Water permeability and compressive strength were tested on hardened concrete specimens and self-healing of cracks over time was observed. Cement paste and CWA paste were prepared to clarify the results obtained on the concrete specimens. SEM and EDS and XRD and FTIR were performed on the hardened pastes to explain the mechanism of CWA working. The results show that the addition of CWA had no significant effect on the compressive strength of the concrete, but reduced the water penetration depth in the concrete, and the reduction was more effective for mixes with lower water–binder ratio. Regarding the self-healing effect, it can be concluded that the addition of CWA improves the crack healing in concrete, but the efficiency of self-healing is highly dependent on the initial crack width. The mechanisms involved in the reduction of water penetration depth and crack healing in concrete can be explained by different mechanisms; one is creation of the CSH gel from unreacted clinker grains, then formation carbonate, and additional mechanism is gel formation (highly expansive Mg-rich hydro-carbonate) from magnesium based additives. The presence of sodium silicate, which would transform into carbonate/bicarbonate, also cannot be excluded.

Topographic characterization of cp-Ti implants with machined and modified surface by LASER

This study characterized the topography osseointegrated implants (cp-Ti) with machined surface (MS), laser beam surface (LS) and laser beam surface followed by deposition of sodium silicate (SS) by means SEM-EDX, roughness measurements, cross-sectional roughness, contact angle, X-ray diffraction (XRD) and laser confocal optical perfilometry. The SEM of MS showed smooth surface, contaminated with machining residues, while LS and SS rough surfaces with a more regular and homogeneous morphological pattern. The EDX showed Ti peaks for MS and Ti and oxygen for LS and SS. The mean roughness values of LS and SS were statistically higher (p <0.05) than MS. The contact angle of LS and SS was 0º. The XRD of MS showed only Ti peaks, while LS and SS showed the presence of oxides and nitrides and presence of sodium silicate. The surface treatment performed in the LS and SS promoted important modifications in the topography and physical-chemical properties.

Silicate-modified oiltea camellia shell-derived biochar: A novel and cost-effective sorbent for cadmium removal

Oiltea camellia shells are a substantial agricultural waste in southern China, but their resource utilization has not been given due attention. In this study, we prepared oiltea camellia shell biochar by pyrolysis (500 °C) in the presence of sodium silicate, and investigated its adsorption capacity for Cd removal. The SEM characterization shows that silicon (Si) is loaded on biochar surfaces as fine particles, and are identified as quartz (SiO2), silicate and C–Si mixture according to X-ray diffraction. Silicate-modification significantly increases (∼45–112%) specific surface area (SSA) and slightly increases (∼5–12%) porosity of biochar. Batch results reveal that Si-modification significantly enhances Cd adsorption, and this increment is more pronounced at pH > 5. Furthermore, silicate-modification promotes the internal diffusion of Cd on biochar. FTIR and XPS analyses suggest that ion exchange with Na+, surface precipitation (CdCO3, CdSiO3 or Cd2SiO4), coordination with π electrons (CC) and complexation with carboxyl and C–Si–O groups are the predominant sorption mechanisms. This study puts a new perspective on the waste utilization of oiltea camellia shells for heavy metal removal from wastewaters or stabilization in contaminated soils.

Controlling lead release due to uniform and galvanic corrosion — An evaluation of silicate-based inhibitors

Silicates have been added to drinking water for decades, both to sequester iron/manganese and as a corrosion control treatment for lead. But the mechanisms by which they might act to limit lead release are not well understood. We evaluated the effects of two silicate formulations on lead release due to uniform and galvanic corrosion over a wide range of pH and dissolved inorganic carbon concentrations. We compared these results to better-characterized systems, with added ortho- or polyphosphate and in an inhibitor-free control. Independent of pH, silicates did not consistently mitigate lead release due to either uniform or galvanic corrosion. Furthermore, lead carbonates appeared to determine lead solubility in the presence of sodium silicate. While silicate treatment did promote the formation of a nanometer-thick silicon layer on lead and a decrease in crystallite size at the scale surface, these changes did not inhibit lead release. But unlike polyphosphate—which is known to form soluble complexes with lead and disperse particulate metals—high ratio silicate did not exacerbate lead release. Metasilicate did exacerbate lead release, especially at pH 7 and 5 mg DIC/L; this suggests that silicate formulation may have an important effect on the dispersion of lead-rich particles.

Electrochemical mechanism and flotation of chalcopyrite and galena in the presence of sodium silicate and sodium sulfite

The electrochemical mechanism involved in the selective separation of chalcopyrite from galena was investigated by flotation and electrochemical methods in the presence of sodium sulfite and sodium silicate, respectively, as a single depressant and their mixture as a combined depressant. Flotation tests revealed that the floatability of chalcopyrite was unaffected by depressants and its recovery remained constant (>80%) within the studied dosage range. Galena flotation was severely depressed with descending depressing order as follows: combined depressant > sodium silicate > sodium sulfite. Electrochemical analysis confirmed the high affinity of depressants on the galena surface, resulting in the formation of hydrophilic species, such as lead sulfite, lead sulfate, and lead orthosilicate. The oxidation of chalcopyrite sutrface and depressants did not exhibit any signals; conversely, the self-oxidation of chalcopyrite was depressed. The results of cyclic voltammograms well agreed with flotation results, demonstrating that chalcopyrite primarily reacted with the collector O-isopropyl-N-ethyl thionocarbamate and that galena mostly reacted with depressants.

Magnesite-dolomite separation using potassium cetyl phosphate as a novel flotation collector and related surface chemistry

To investigate the separation effect of magnesite from dolomite using potassium cetyl phosphate (PCP) as a collector, flotation experiments were carried out. In this study, the results obtained from the single minerals experiments showed an excellent selectivity with high recoveries for magnesite using PCP as the collector in contrast to the case with dolomite. The separation effect of the binary mixtures at pulp pH 9.0 was also investigated. The results confirmed that the PCP is an appropriate collector for the flotation separation of magnesite from dolomite. Surface chemical aspects of the separation mechanism were investigated through measurements of zeta potential, contact angle, and X-ray photoelectron spectroscopy analysis. The results support the flotation selectivity observed and are consistent with chemisorption of PCP on magnesite in the presence of sodium silicate that was used as a modifier to stabilize hydrophilicity of dolomite and remove its adverse effect on the recovery of magnesite.

Selective flotation of magnesite from calcite using potassium cetyl phosphate as a collector in the presence of sodium silicate

In this communication, we report the flotation behavior of magnesite and calcite using potassium cetyl phosphate (PCP) as a novel anionic collector. The results of the single mineral experiments showed an excellent natural selectivity between the two minerals unlike the flotation of their binary mixture that required the use of sodium silicate as a modifier. Results from zeta potential measurements are also reported in relation to the adsorption mechanism of this selective flotation system. It has been concluded that PCP is an appropriate collector for the flotation separation of magnesite from calcite.

Recovery of rare earth elements minerals from iron oxide–silicate rich tailings – Part 2: Froth flotation separation

This study is the second part of an ongoing investigation to recover and upgrade rare earth elements (REE) minerals from iron oxide–silicate rich tailings (IST) generated at a South Australian mining operation. Previous work (Part 1) has shown that REE minerals are preconcentrated in a high-intensity magnetic concentrate and non-magnetic tails along with iron oxides and silicate minerals, respectively. As a part of the overall beneficiation and enhanced REE minerals recovery strategy, complementary studies involving downstream froth flotation of the magnetic preconcentrates were conducted and the results presented in this paper. Froth flotation of the preconcentrates was carried out using sodium oleate and hydroxamic acid as collectors in the presence of sodium silicate and starch as depressants. A comparison of rougher flotation of the preconcentrates indicated that hydroxamic acid produced higher total rare earth oxides (TREO) recoveries (91–93%) with enrichment ratio ranging 1.03–1.30, whereas sodium oleate produced relatively higher upgrade (1.50–1.55 ratios) with significantly lower recoveries (12–36%). Scavenger and cleaner flotation tests were conducted on selected concentrates and tails, where further upgrade was achieved at the expense of recovery. Two process flowsheets for recovering REE minerals were then developed. Flowsheet 1 includes magnetic preconcentration followed by flotation using both collectors, whilst Flowsheet 2 includes magnetic preconcentration prior to hydroxamic acid flotation. Typical metallurgical results indicated Flowsheet 1 produced a final concentrate grade of 1.55% at 55% TREO recovery, whilst rejecting 47% Fe and 74% Si, whereas a final concentrate grade of 1.67% at 72% TREO recovery, with 39% Fe and 59% Si removed using Flowsheet 2. The REE minerals, in combination with mainly silicates in the non-magnetic tails, allows better upgrade, with 2.5 times enrichment through hydroxamic acid flotation, compared to 1.93 times enrichment from the REE–iron oxides magnetic preconcentrate. Florencite, which was not recovered and upgraded by magnetic separation, was successfully recovered and upgraded along with bastnäsite and monazite by froth flotation. The study has revealed that froth flotation can be used to complement the recovery of REE minerals by magnetic separation, suggesting the IST could be exploited for REE beneficiation. However, it is obvious that minerals liberation and particle size distribution are critical in achieving enhanced REE minerals recovery and upgrade.

Synthesis of mesoporous silica microspheres by a spray-assisted carbonation microreaction method

A novel spray-assisted carbonation microreaction method for the synthesis of mesoporous silica microspheres is reported. The synthetic process comprises the preparation of a silica sol via a carbonation reaction, rapid gelation at high temperature, and subsequent rapid solvent evaporation by spray drying. The carbonation microreaction was conducted in a membrane dispersion microreactor, in the presence of sodium silicate and carbon dioxide reactants. The as-synthesized silica microspheres exhibit a uniform mesostructure, excellent dispersity, and a narrow particle size distribution, with average diameters of 1–2μm, Brunauer–Emmett–Teller surface areas of 300–1149m2/g, and total pore volumes of 0.21–1.82cm3/g. Relatively low concentrations of the silicate species and well-controlled silica condensation rates are responsible for the formation of the observed spherical morphology. The synthetic process is of significant practical importance as a result of using low-cost raw materials, and because of the excellent controllability and process stability displayed. Furthermore, this rapid and flexible method may be extended to the synthesis of various silica materials and their composites.

A fundamental study of chalcopyrite flotation in sea water using sodium silicate

Due to the shortage of fresh water, sea water has been considered as a promising alternative for mineral flotation. Sodium silicate (SS) was used to eliminate the negative influence due to the application of sea water for chalcopyrite flotation and the related mechanisms were studied. Flotation results showed that the most detrimental compound in sea water was the divalent ion of Mg2+. Contact angle measurements suggested that SS increased chalcopyrite hydrophobicity in sea water and MgCl2 solution. The zeta potential of chalcopyrite became more negative while that of Mg(OH)2 was reversed from positive to negative upon the addition of SS, preventing the adsorption of hydrophilic Mg(OH)2 precipitates on chalcopyrite surface. FTIR and XPS analyses further confirmed that the presence of SS in sea water reduced the adsorption of Mg(OH)2 on chalcopyrite surface. In addition, Derjguin-Landau-Verwey-Overbeek (DLVO) calculation indicated that SS can prevent the adsorption of Mg(OH)2 on chalcopyrite surface, thereby increasing chalcopyrite recovery. Therefore, this study presents an effective method to improve chalcopyrite flotation recovery in sea water.

A systematic study on polymer modified alkali-activated slag – Part I: Stability analysis of colloidal polymer dispersion in sodium water glass

Colloidal stability of polymer particles in activator is the pre-condition for the application of polymer dispersion in alkali activated materials (AAM). In this study, investigation of the stability of classical cement-stable polymers (styrene acrylate (SA) and ethylene-vinyl acetate (EVA)) in the presence of sodium silicate with different moduli at varied dosages and storing times was conducted through combined techniques including laser particle analysis and ultraviolet-visible spectrophotometry (UV–Vis). It is found that SA is significantly more stable than EVA dispersions. Dosage of sodium silicate and storing time are the main factors for loss of colloidal stability of the polymer particles. The highest colloidal stability of the latexes was observed with the lowest investigated modulus (M < 1.81). Sodium sulphate alone or a combination of sodium sulphate and hydroxide ions have no effect on the colloidal stability of polymer particles. However, in the presence of sodium silicate, sodium sulphate greatly decreases the colloidal stability.

Time-Dependent Growth of Silica Shells on CdTe Quantum Dots.

The purpose of this study is to investigate the time dependent growth of silica shells on CdTe quantum dots to get their optimum thicknesses for practical applications. The core/shell structured silica-coated CdTe quantum dots (CdTe/SiO2 QDs) were synthesized by the Ströber process, which used CdTe QDs co-stabilized by mercaptopropionic acid. The coating procedure used silane primer (3-mercaptopropyltrimethoxysilane) in order to make the quantum dots (QDs) surface vitreophilic. The total size of QDs was dependent on both the time of silica shell growth in the presence of sodium silicate, and on the presence of ethanol during this growth. The size of particles was monitored during the first 72 h using two principally different methods: Dynamic Light Scattering (DLS), and Scanning Electron Microscopy (SEM). The data obtained by both methods were compared and reasons for differences discussed. Without ethanol precipitation, the silica shell thickness grew slowly and increased the nanoparticle total size from approximately 23 nm up to almost 30 nm (DLS data), and up to almost 60 nm (SEM data) in three days. During the same time period but in the presence of ethanol, the size of CdTe/SiO2 QDs increased more significantly: up to 115 nm (DLS data) and up to 83 nm (SEM data). The variances occurring between silica shell thicknesses caused by different methods of silica growth, as well as by different evaluation methods, were discussed.

A study of selective flotation recovery of rare earth oxides from hematite and quartz using hydroxamic acid as a collector

Monazite is a major rare earth elements (REE)-bearing phosphate mineral predominantly found in association with hematite and quartz in some Australian rare earth deposits. The flotation of rare earth oxides (REO) in monazite from mixtures containing monazite, hematite, and quartz with hydroxamic acid as a collector has been investigated using an IMN microflotation cell and a 1.2 L Denver flotation cell. Maximum flotation recovery of both monazite and hematite was attained at pH 7, whereas that of quartz, at pH 3. The flotation kinetics data indicated the need for depressants to achieve selective REO recovery from hematite and quartz mixtures. Sodium silicate and starch were thus tested as depressants of both hematite and quartz. The separation efficiency of REO in the absence of depressants was low and averaged 6.42% at 99% REO recovery, but could be increased to 44.78% with corresponding 93% REO recovery when 4000 g/t starch was used. However, the efficiencies of REO separation obtained with sodium silicate were generally lower (<18%), due to higher gangue minerals content in the flotation concentrates. A blend of sodium silicate and starch showed a good performance for REO recovery, with enhanced selectivity against hematite and quartz through a rougher-cleaner flotation test. This study presents the feasibility of upgrading REO from iron-oxide rich tailings using hydroxamic acid, in the presence of sodium silicate and starch as depressants.

Influence of selected parameters on compressive strength of geopolymer produced from ground glass fiber

In this study, ground glass fiber (GGF), manufactured by milling waste glass fiber, was used to produce geopolymer mixtures. The effect of using different alkali content and different combinations of alkali activator solutions on the compressive strength and micro-structure of GGF-based geopolymer mixtures were investigated and compared with fly ash-based geopolymer mixtures. Furthermore, the effect of temperature (from ambient to 110°C) and duration of heat-curing on the compressive strength and micro-structure of GGF-based geopolymers was studied. Results of this study showed that for all the levels of alkali content, GGF-based geopolymers showed a higher compressive strength in comparison to the fly ash-based specimens; prepared with a same solution and heat-curing method. It was also seen that the strength gain in GGF-based geopolymers does not depend on the presence of sodium silicate in the activator solution; and high compressive strength (as high as 80MPa) can be achieved by using sodium hydroxide solution alone. The temperature of heat curing was also seen to affect the early-age (i.e. 3–7days) strength of the GGF-based samples, but had no significant effect on the later-age (i.e. 28–56days) strength. Finally, it was concluded that GGF has a good potential to be used as a precursor to produce high strength geopolymers even at the low curing temperatures as the ambient temperature (23°C).

In situ preparation and stabilization of silver nanoparticles-water glass composite

Water glass – silver nanoparticles composite was prepared by simple reduction method of in situ prepared silver hydroxide by ascorbic acid in presence of sodium silicate. Various shapes and forms were produced by treatment of formed dispersion by carbon dioxide. Prepared material was characterised by Vis spectroscopy, scanning electron microscopy - energy dispersive X-ray spectroscopy and X-ray powder diffraction. Average diameter of silver nanoparticles was 22nm. Chemicals used have no or low toxicity and are affordable and environmentally friendly. The method is to use in various applications where long-term stable silver nanoparticles in easily shapeable solid matrix are desired.